Legacy Modernization Pattern — MCP recommendations

Pattern: Legacy Modernization
Component: mcps.md
Version: 1.1 | Updated: 2026-07-29

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Purpose

Least-privilege MCP servers for the Legacy Modernization pattern. Keep mcpServers: {} until a human enables stubs after MCP when and how.

Recommended MCPs

MCP	Why for this pattern
GitHub	History and PR evidence
Filesystem	Legacy tree reads

When to enable for Legacy Modernization

Filesystem reads the legacy tree; GitHub supplies history. No deploy MCP until a strangler slice has characterization coverage.

Enable rules (this pattern)

1. Legacy modernization MCPs stay read-only during discovery
2. Never commit tokens; map secrets outside git
3. Record allowlist + data class in MODEL_POLICY / SoA before write tools
4. Do not enable write MCP across both legacy and modern trees in one session

Anti-patterns

• Rewriting modules discovered only via unranked MCP search
• Deleting legacy paths through tools without golden-test proof
• Mixing modernization and migration cutover tools in one agent turn

Checklist

• Legacy Modernization MCPs mapped to env secrets outside git
• Unused servers remain disabled after the legacy modernization gate
• Injection / tool PEP reviewed if tools can act